Ultra Narrow Band Filter: Production of Long Wave Infrared Ultra Narrow Band Filter
The first channel long wave infrared ultra narrowband filter of the atmospheric detection infrared spectrometer is specifically designed to detect the concentration of CO2 gas in the atmosphere. Therefore, the optical performance of the filter should be designed based on the characteristic absorption peak of CO2 gas in the atmosphere
According to the absorption characteristic peak of CO2 gas in the atmospheric environment, the main technical specifications of the first channel filter in the NOAA series atmospheric infrared radiometer in the United States are: center wavelength of 14.95um, bandwidth of 0.067um. In order to make the scale of China's spaceborne atmospheric vertical detection infrared spectrometer possibly smaller, the overall design personnel did not use the aberration reducing thick lens scheme from abroad in front of the detector, but used a composite curved reflector condenser designed by non imaging technology. Therefore, the half cone angle of the incident filter beam reached 18 degrees.
The design of ultra narrowband filter adopts the principle of all dielectric Fabry Perot filter design. When the incident beam is a conical shape with a half cone angle, the performance of the filter is obtained by integrating the transmittance curve over all incident angles. The bandwidth of the filter is the half width of the filter when the beam is vertically incident. As the incident angle increases, the transmittance of the filter decreases, and the center wavelength shifts towards shorter wavelengths, resulting in an increase in the half width. Therefore, in order to achieve spectral performance of infrared long wave ultra narrow band filters with half cone angle beam incidence parallel to the beam, the development of the filter has certain difficulties.
The performance requirements for long wave infrared ultra narrowband filter technology are very high, requiring strict control of process parameters. Control factors such as temperature and humidity in the production environment, substrate temperature, placement of coating materials, and evaporation rate. In addition, the selection of high-quality film materials is extremely important
According to the absorption characteristic peak of CO2 gas in the atmospheric environment, the main technical specifications of the first channel filter in the NOAA series atmospheric infrared radiometer in the United States are: center wavelength of 14.95um, bandwidth of 0.067um. In order to make the scale of China's spaceborne atmospheric vertical detection infrared spectrometer possibly smaller, the overall design personnel did not use the aberration reducing thick lens scheme from abroad in front of the detector, but used a composite curved reflector condenser designed by non imaging technology. Therefore, the half cone angle of the incident filter beam reached 18 degrees.
The design of ultra narrowband filter adopts the principle of all dielectric Fabry Perot filter design. When the incident beam is a conical shape with a half cone angle, the performance of the filter is obtained by integrating the transmittance curve over all incident angles. The bandwidth of the filter is the half width of the filter when the beam is vertically incident. As the incident angle increases, the transmittance of the filter decreases, and the center wavelength shifts towards shorter wavelengths, resulting in an increase in the half width. Therefore, in order to achieve spectral performance of infrared long wave ultra narrow band filters with half cone angle beam incidence parallel to the beam, the development of the filter has certain difficulties.
The performance requirements for long wave infrared ultra narrowband filter technology are very high, requiring strict control of process parameters. Control factors such as temperature and humidity in the production environment, substrate temperature, placement of coating materials, and evaporation rate. In addition, the selection of high-quality film materials is extremely important